應用反應曲面法於具分流流道質子交換膜燃料電池參數最佳化設計

Optimal Design of Operation Parameters on the Performance of Proton Exchange Membrane Fuel Cells Using Response Surface Methodology

質子交換膜燃料電池具有高效率能量轉換、低溫操作及環保潔淨等優點，而燃料電池之反應需以固態高分子膜為電解質，透過保持適當的運轉溫度及濕度，增進其離子導電度，以產生最大效能。燃料電池反應過程中，隨著電池內部的反應速率提升，濃度極化現象會越加明顯，且此一現象會逐漸往上游蔓延，同時越小之氣體流量也會導致濃度極化現象提早發生，當氣體不足以供應流道末端反應，產生濃度不均勻現象則會造成電池性能下降。本研究透過所設計的多孔型單一蛇型流道，除了原有傳統流道入口之外，另以不同分流供氣位置注入氧氣，期望減少流道內反應氣體與產物在不同位置的濃度差異，以提升反應放電的效能，降低不均勻性，並輔以不同的操作溫度及氣體流量比較與原始未分流流道的性能表現，探討多孔型流道加入分流後的電流密度變化及性能表現。本研究並藉由反應曲面法，建立具分流流道質子交換膜燃料電池性能影響之主要操作參數二階迴歸方程式，最後由實驗設計結果所得之最佳參數為分別為燃料電池的工作溫度59.98°C、陽極加濕溫度68.92°C、陽極流率255.37SCCM、陰極流率309.15 SCCM、分流流率70.96 SCCM與分流位置33.17%，而預測之最大輸出功率P 值為21.57 W，經由統計分析獲得最佳操作參數設定，進而產出較高燃料電池輸出功率。

The proton exchange membrane fuel cell possesses the merits of highefficiency of energy conversion, low operating temperature and nopollution. It uses a solid polymer membrane as the electrolyte for cellreaction, and the ions conductivity are enhanced through the control ofproper operation temperature and humidification. As the output currentincreases during reaction of a fuel cell, the concentration polarizationphenomenon emerges around downstream region of the channel, and itexpands gradually toward upstream. This phenomenon is obvious whenthe reactant flow rate is insufficient to supply the cell reaction. It causes aserious non-uniform distribution of reaction and deteriorates overall cellperformance.In this study, a cathode flow field is designed with an additional port asinlet split point. Besides the original inlet port, the reactant gas can besupplied from this split point in order to reduce the maldistribution ofreactant and product concentration. The effects of the split point positionand split flow rate on the polarization curve is discussed and comparedwith those of traditional flow fields at various operating conditions.The results show that a suitable split flow rate around the frontalregion of flow channel has a positive effect on cell performance when thecell voltage is low. Therefore, this study reveals that, through theexperiments at different temperature and flow ratio setting, the uniform cellreaction is achieved by using the split flow field in a PEMFC. Also byusing the Response Surface Methodology (RSM), prediction model ofmajor operation parameters influencing the performance of a PEMFC witha split flow field is developed. The optimal parameters are: operatingtemperature 59.98℃, anode humidification temperature 68.92℃, anodeflow rate 255.37 SCCM, cathode flow rate 309.15 SCCM, split flow rate70.96 SCCM and split point 33.17%.